When trying to figure out how much does a 4 horse trailer weigh, you can’t put them all at the same weight, as different brands and models mean a variation.
The lightest horse trailers are aluminum. It is very common for modern trailers to use this material, as it avoids rust and makes everything lighter than steel.
To answer the question of how much does a 4 horse trailer weigh is impossible to pinpoint, but you can get an idea of the range, as we pointed out here. Don’t assume that if you see your truck has a towing capacity of 9,000 pounds, that it can actually pull a 5,000-pound four-horse trailer.